Prime Minister Sir Keir Starmer has been warned by Lord Hermer, the Attorney General, that UK participation in a potential US military strike on Iran may be unlawful under international law.
Legal advice reportedly issued by Hermer suggests Britain must limit its role to defending allies rather than participating in offensive operations.
The warning comes as speculation grows that President Donald Trump may soon authorise military action against Iran, potentially using UK-based military assets.
Recall that at a Cobra emergency committee meeting on Wednesday, Starmer and senior ministers discussed Britain’s options should Trump choose to intervene in the ongoing conflict between Israel and Iran.
UK military contributions under consideration include air and maritime support in the Gulf, defensive operations like intercepting drones targeting Israel, or more direct action such as launching submarine missiles at Iran.
However, Lord Hermer is reportedly reluctant to sign off on any role beyond defensive support. A government official said “The AG has concerns about the UK playing any role in this except for defending our allies.”
Mounting concerns in London follow reports that the US may use B-2 Spirit stealth bombers based at Diego Garcia, a joint US-UK airbase in the Indian Ocean.
American plans also involve deploying refuelling aircraft in Spain and Greece. Although the UK must approve any US operations launched from Diego Garcia, it is understood that no formal request has yet been made.
In parallel, Britain has bolstered its military presence in the region, sending six additional Typhoon jets to RAF Akrotiri in Cyprus. Further deployments may be considered if the conflict escalates. Sources also suggest the US may ask to use Akrotiri for operations supporting Israel, though no clear plan has emerged from Washington, Jerusalem, or Tehran.
Despite Trump’s public ambiguity, saying, “I may do it, I may not do it. Nobody knows what I’m going to do”, media reports indicate that attack plans have been finalized, pending Iran’s response to US demands to abandon its nuclear programme. Trump added that next week could see very big developments.
Meanwhile, the UK government appears focused on avoiding escalation. Work and Pensions Secretary Liz Kendall told the BBC that diplomacy remained the priority: “The nature of diplomacy is that you fail every day until you succeed. That is why we are absolutely focused on that message.” A Downing Street spokesperson reiterated that Britain’s stance is to de-escalate rather than escalate.
Foreign Secretary David Lammy has flown to Washington for urgent talks with US Secretary of State Marco Rubio, while Lord Mandelson and the UK ambassador to the US also attended the Cobra meeting, which included updates on diplomatic efforts and the safety of British nationals in the region.
Lord Hermer’s role is attracting renewed scrutiny, with critics accusing him of slowing down government business by insisting on rigorous human rights compliance in legislation. His cautious stance on military legality echoes the controversy over Lord Goldsmith’s legal advice ahead of the 2003 Iraq War, when the then-Attorney General initially deemed the war illegal before reversing his position under political pressure.
Hermer has also faced criticism for declining to challenge lenient sentences in high-profile cases, while prosecuting others under contentious circumstances. Earlier this year, he was accused of comparing political threats to abandon international legal commitments to the actions of 1930s Nazi Germany.
Asked to confirm the content of the Attorney General’s legal advice, a spokesperson said: “By long-standing convention, reflected in the ministerial code, whether the law officers have been asked to provide legal advice and the content of any advice is not routinely disclosed. The convention provides the fullest guarantee that government business will be conducted at all times in light of thorough and candid legal advice.”
On the ground, the situation is rapidly worsening. Israel launched fresh strikes on Tehran this week, targeting internal security headquarters, while Iran’s retaliation has been less effective, with just 10 missiles intercepted by Israel’s Iron Dome on Tuesday night. Human Rights Activists, a US-based group, reported that 585 people have been killed in Iran by Israeli bombardment, including 239 civilians. In response, Iran has launched over 400 missiles and hundreds of drones, killing at least 24 people in Israel.
Iran’s Supreme Leader, Ayatollah Ali Khamenei, dismissed US threats on state television, calling Trump’s ultimatum unacceptable and warning that “threats will not affect the thinking and behaviour of the Iranian nation.”
Amidst these developments, Trump left the G7 summit in Canada early, citing big stuff that required his attention further fuelling speculation of imminent US military involvement. A Pentagon spokesperson said on Wednesday: “Protecting US forces is our top priority and these deployments are intended to enhance our defensive posture in the region.”
As the UK navigates its role in a fast-developing crisis, Lord Hermer’s legal position may prove pivotal in shaping how far Britain is willing to go in supporting its closest ally.
